This invention relates to improvements in three-way solenoid valves for controlling the flow of a fluid. Such valves are used to direct the flow of fluid along one pathway when the solenoid is actuated or energized, and along another pathway when it is not actuated or is de-energized.
Typically, such valves have required springs and internal working seals, and they have been neither compact nor readily modifiable.
Heretofore, it has been necessary to design and construct normally open solenoid valves differently from normally closed valves. Such differences have required that almost every part for the normally open valve be different from the generally corresponding part of the normally closed valve, thus requiring that greater inventories of parts be kept on hand for manufacturing the actual valves.
The present invention solves these problems by providing solenoid valves of both normally open and normally closed types, in which most of the parts are identical and which may be readily converted to one or the other, all without otherwise altering the physical or operational characteristics of the valve in either form. Furthermore, the modification of the valve is done without significant expense of time or resources.
The valve of the present invention may be employed wherever a three-way solenoid valve is needed. For example, it has been found a useful component in a hydromechanical transmission, such as the one described in U.S. Pat. Nos. 4,008,628 and 4,134,311. There, this valve may be used to control the flow of hydraulic fluid into a hydraulic cylinder which engages various parts of the transmission and directly varies vehicle speed. Release of the fluid from the hydraulic cylinder is also controlled by the valve.